#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>

int fbi(int n) 
{
	if (n <= 1)return n;
	else return fbi(n - 1) + fbi(n - 2);
}


int main() 
{
	int i;
	scanf("%d",&i);
	printf("%d", fbi(i));

}